Compositions of 1-bromopropane, nitromethane or acetonitrile and an alcohol

ABSTRACT

The invention relates to novel compositions of 1-bromopropane, nitromethane or acetonitrile and at least one alcohol selected from the group consisting of ethanol, 2-propanol and 2-methyl-2-propanol and more particularly to azeotrope-like compositions based on these compounds which are useful as solvents in refrigeration flushing, oxygen system cleaning and vapor degreasing applications.

FIELD OF THE INVENTION

This invention relates to compositions of 1-bromopropane, nitromethaneor acetonitrile and at least one alcohol and more particularly toazeotrope-like compositions based on these compounds. These mixtures areuseful as solvents for use in refrigeration flushing, oxygen systemcleaning, and vapor degreasing applications including electronicscleaning.

BACKGROUND OF THE INVENTION

1-Bromopropane based fluids have found widespread use in industry forsolvent cleaning, i.e. vapor degreasing, cold cleaning and ultrasoniccleaning of complex metal parts, circuit boards, electronic components,implantable prosthetic devices, optical equipment and others.

In its simplest form, vapor degreasing or solvent cleaning consists ofexposing a room temperature object to be cleaned to the vapors of aboiling solvent. Vapors condensing on the object provide clean distilledsolvent to wash away grease or other contaminants. Final evaporation ofthe solvent from the object leaves no residue on the object.

For difficult to remove soils where elevated temperature is necessary toimprove the cleaning action of the solvent, or for large volume assemblyline operations where the cleaning of metal parts and assemblies must bedone efficiently, a vapor degreaser is employed. The conventionaloperation of a vapor degreaser consists of immersing the part to becleaned in a sump of boiling solvent which removes the bulk of the soil,thereafter immersing the part in a sump containing freshly distilledsolvent near room temperature, and finally exposing the part to solventvapors over the boiling sump which condense on the cleaned part. Thepart can also be sprayed with distilled solvent before final rinsing.

Azeotropic or azeotrope-like compositions are particularly desiredbecause they do not fractionate upon boiling. This behavior is desirablebecause in the previously described vapor degreasing equipment in whichthese solvents are employed, redistilled material is generated for finalrinse-cleaning. Thus, the vapor degreasing system acts as a still.Unless the solvent composition exhibits a constant boiling point, i.e.,is azeotrope-like, fractionation will occur and undesirable solventdistribution may act to upset the cleaning and safety of processing.

The art is continually seeking new solvent mixtures which offeralternatives for the above-described applications. Currently,environmentally acceptable materials are of particular interest becausethe traditionally used fully halogenated chlorocarbons andchlorofluorocarbons have been implicated in causing environmentalproblems associated with the depletion of the earth's protective ozonelayer. Mathematical models have substantiated that 1-bromopropane willnot adversely affect atmospheric chemistry because its contribution tostratospheric ozone depletion and global warming in comparison to thefully halogenated chlorocarbons and chlorofluorocarbons species isnegligible. The ozone depletion potential of 1-bromopropane is0.002-0.03, which is significantly lower than the ozone depletionpotentials of 1,1,2-trichloro-1,2,2-trifluoroethane or CFC-113 (0.8) and1,1-dichloro-1-fluoroethane or HCFC-141 b (0.11). The global warmingpotential of 1-bromopropane (0.31) is also significantly lower thanCFC-113 (5000) and HCFC-141b (630).

The art has also looked to compositions which include components whichcontribute additionally desired characteristics, such as polarfunctionality, increased solvency power, and stabilizers while retainingthose properties exhibited by the prior art chlorofluorocarbonsincluding chemical stability, low toxicity, and non-flammability.

It is accordingly an object of this invention to provide novel ternarycompositions based on 1-bromopropane, nitromethane or acetonitrile andat least one alcohol, and preferably azeotrope-like compositions, whichare useful in solvent and other applications and which meet the abovecriteria.

The present compositions are advantageous for the following reasons. The1-bromopropane component has an ozone depletion potential of 0.002-0.03and has reasonable solvency characteristics. The alcohol has goodsolvent properties to enable the cleaning and dissolution of ionics,flux resin and oils. The nitromethane or acetonitrile component is knownto inhibit the decomposition of 1-bromopropane. Thus, when thesecomponents are combined in effective amounts, an efficient, stable,environmentally acceptable solvent composition results.

DESCRIPTION OF THE INVENTION

The invention relates to novel compositions comprising effective amountsof 1-bromopropane, nitromethane or acetonitrile, and at least onealcohol selected from the group consisting of ethanol, 2-propanol and2-methyl-2-propanol. The invention further relates to azeotrope-likecompositions comprising from about 65 to about 99 weight percent1-bromopropane; from about 1 to about 35 weight percent nitromethane oracetonitrile; and, based on the total weight of said 1-bromopropane andnitromethane or acetonitrile, from about 1 to about 35 weight percent ofat least one alcohol selected from the group consisting of ethanol,2-propanol and 2-methyl-2-propanol, which compositions boil at fromabout 60.2° C. to about 67.5° C.±about 2.0° C. at 760 mmHg.

The 1-bromopropane, nitromethane, acetonitrile and alcohol components ofthe invention are commercially available in pure form and may beobtained readily.

The term "azeotrope-like" is used herein for the preferred mixtures ofthe invention because in the claimed proportions, the compositions of1-bromopropane, nitromethane or acetonitrile and at least one alcoholare constant boiling or essentially constant boiling. All compositionswithin the indicated ranges, as well as certain compositions outside theindicated ranges, are azeotrope-like, as defined more particularlybelow.

From fundamental principles, the thermodynamic state of a fluid isdefined by four variables: pressure, temperature, liquid composition,and vapor composition, or P-T-X-Y, respectively. An azeotrope is aunique characteristic of a system of two or more components where X andY are equal at a stated P and T. In practice, this means that thecomponents cannot be separated during a phase change, and therefore areuseful in solvent and aerosol solvent applications.

For the purposes of this discussion, by azeotrope-like composition isintended to mean that the composition behaves like a true azeotrope interms of its constant boiling characteristics or tendency not tofractionate upon boiling or evaporation. Thus, in such systems, thecomposition of the vapor formed during evaporation is identical orsubstantially identical to the original liquid composition. Hence duringboiling or evaporation the liquid composition changes, if at all, onlyslightly. This is contrasted with non-azeotrope-like compositions inwhich the liquid and vapor compositions change substantially duringevaporation or condensation.

One way to determine whether a candidate mixture is azeotrope-likewithin the meaning of this invention, is to distill a sample thereofunder conditions (i.e., resolution--number of plates) which would beexpected to separate the mixture into its separate components. If themixture is not an azeotrope or azeotrope-like, the mixture willfractionate, i.e., separate into its various components with the lowestboiling component distilling off first, and so on. If the mixture isazeotrope-like, some finite amount of the first distillation cut will beobtained which contains all of the mixture components and which isconstant boiling or behaves as a single substance. This phenomenoncannot occur if the mixture is not azeotrope-like, i.e., if it is notpart of an azeotrope system.

It follows from the above that another characteristic of azeotrope-likecompositions is that there is a range of compositions containing thesame components in varying proportions which are azeotrope-like. Allsuch compositions are intended to be covered by the term azeotrope-likeas used herein. As an example, it is well known that at differentpressures the composition of a given azeotrope will vary at leastslightly as does the boiling point of the composition. Thus, anazeotrope of A and B represents a unique type of relationship but with avariable composition depending on the temperature and/or pressure. As isreadily understood by persons skilled in the art, the boiling point ofan azeotrope will vary with the pressure.

In the process embodiment of the invention, the compositions of theinvention may be used to clean solid surfaces by treating said surfaceswith said compositions in any manner well known in the art such as bydipping or use of open or closed vapor degreasing apparatus.

It should be understood that the present compositions may include one ormore additional components (such as stabilizers, inhibitors orantioxidants), some of which may form new azeotrope-like compositions.Such additional components typically are added at the expense of1-bromopropane and in amounts known to one skilled in the art.Preferably, such components are added in an amount of up to about 5weight percent based on the weight of the 1-bromopropane component, andmore preferably in an amount of up to about 5 weight percent based onthe total weight of the composition. Any such compositions areconsidered to be within the scope of the present invention as long asthe compositions contain all of the essential components describedherein.

Stabilizers typically are added to solvent compositions to inhibitdecomposition of the compositions; react with undesirable decompositionproducts of the compositions; and/or prevent corrosion of metalsurfaces. Any combination of conventional stabilizers known to be usefulin stabilizing halogenated hydrocarbon solvents may be used in thepresent invention. Suitable stabilizers include alkanols having 4 to 7carbon atoms, nitroalkanes having 1 to 3 carbon atoms, 1,2-epoxyalkaneshaving 2 to 7 carbon atoms, phosphite esters having 12 to 30 carbonatoms, ethers having 3 or 4 carbon atoms, unsaturated compounds having 4to 6 carbon atoms, acetals having 4 to 7 carbon atoms, ketones having 3to 5 carbon atoms, and amines having 6 to 8 carbon atoms. Other suitablestabilizers will readily occur to those skilled in the art. See, forexample, U.S. Pat. No. 5,665,172.

The present invention is more fully illustrated by the followingnon-limiting Examples.

EXAMPLES

The range over which the following compositions exhibit constant boilingbehavior was determined using ebulliometry and then confirmed bydistillation.

The ebulliometer used in this experiment consisted of a heated sump. Theupper part of the ebulliometer connected to the sump was cooled therebyacting as a condenser for the boiling vapors, allowing the system tooperate at total reflux. Measured quantities of the lower boilingmaterial was charged into the ebulliometer and brought to a boil. Then,in separate identical experiments, measured amounts of the relevant highboiling component was titrated into the ebulliometer. The change inboiling point was measured with a platinum resistance thermometer.

A 5-plate Oldershaw distillation column with a cold water condensedautomatic liquid dividing head was used to confirm the composition ofthe azeotrope-like compositions. The distillation column was chargedwith 1-bromopropane, nitromethane or acetonitrile and an alcohol and thecomposition was heated under total reflux for about an hour to ensureequilibration. A reflux ratio of 5:1 was employed. Approximately 50percent of the original charges were collected in four similar-sizedoverhead fractions. The compositions of these fractions were analyzedusing Gas Chromatography and are reported in the tables below.

The preferred and more preferred embodiments for each azeotrope-likecomposition of the invention are listed in the following tables. Theproportions/ranges listed are understood to be prefaced by "about".

                  TABLE I                                                         ______________________________________                                        Preferred Compositions                                                                           C                                                            A              B     (wt. % based on total weight   Boiling Point                                              (wt.%)        (wt.%)     A + B)                                                      (° C. at 760 mmHg)           ______________________________________                                        89-99% 1-11%   1-10% 2-Methyl-2-Propanol                                                                      67.5 ± 2.0                                   1-Bromo- Nitro-                                                               propane            methane                                                    89-99%     1-11%     5-25% 2-Propanol              64.9 ± 2.0                                             1-Bromo-     Nitro-                            propane          methane                                                      65-92%      8-35%    1-35% 2-Methyl-2-Propanol     64.1 ± 2.0                                             1-Bromo-        Aceto-                         propane             nitrile                                                   65-92%      8-35%    5-30% Ethanol                60.2 ± 2.0                                              1-Bromo-      Aceto-                           propane         nitrile                                                     ______________________________________                                    

                  TABLE II                                                        ______________________________________                                        More Preferred Compositions                                                                      C                                                            A              B     (wt. % based on total weight   Boiling Point                                              (wt.%)        (wt.%)     A + B)                                                      (° C. at 760 mmHg)           ______________________________________                                        92-99% 1-8%    1-7% 2-Methyl-2-Propanol                                                                       67.5 ± 1.0                                   1-Bromo- Nitro-                                                               propane            methane                                                    92-99%     1-8%     7-20% 2-Propanol              64.9 ± 1.0                                              1-Bromo-     Nitro-                            propane          methane                                                      75-90%      10-25%    4-32% 2-Methyl-2-Propanol     64.1 ± 1.0                                            1-Bromo-        Aceto-                         propane             nitrile                                                   75-90%      10-25%    10-30% Ethanol                60.2 ± 1.0                                            1-Bromo-      Aceto-                           propane         nitrile                                                     ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        Most Preferred Compositions                                                                      C                                                            A              B     (wt. % based on total weight   Boiling Point                                              (wt.%)        (wt.%)     A + B)                                                      (° C. at 760 mmHg)           ______________________________________                                         99%   1%      3% 2-Methyl-2-Propanol                                                                         67.5 ± 0.5                                   1-Bromo- Nitro-                                                               propane            methane                                                    95%     5%     10-15% 2-Propanol              64.9 ± 0.5                   1-Bromo-     Nitro-                                                           propane          methane                                                      82%      18%    6-30% 2-Methyl-2-Propanol     64.1 ± 0.5                   1-Bromo-        Aceto-                                                        propane             nitrile                                                   82%      18%    15-21% Ethanol                60.2 ± 0.5                   1-Bromo-      Aceto-                                                          propane         nitrile                                                     ______________________________________                                    

What is claimed:
 1. Azeotrope-like compositions consisting essentiallyof from about 89 to about 99 weight percent 1-bromopropane; from about 1to about 11 weight percent nitromethane; and, based on the total weightof said 1-bromopropane and nitromethane, from about 1 to about 10 weightpercent 2-methyl-2-propanol wherein said compositions boil at 67.5°C.±2.0° C. at 760 mmHg.
 2. Azeotrope-like compositions of claim 1consisting essentially of from about 92 to about 99 weight percent1-bromopropane; from about 1 to about 8 weight percent nitromethane;and, based on the total weight of said 1-bromopropane and nitromethane,from about 1 to about 7 weight percent 2-methyl-2-propanol wherein saidcompositions boil at 67.5° C.±1.0° C. at 760 mmHg.
 3. The azeotrope-likecompositions of claim 1 consisting essentially of about 99 weightpercent 1-bromopropane; about 1 weight percent nitromethane; and, basedon the total weight of said 1-bromopropane and nitromethane, about 3weight percent 2-methyl-2-propanol wherein said compositions boil at67.5° C.±0.5° C. at 760 mmHg.
 4. A method for cleaning a surface of asubstrate which comprises treating said surface with a composition ofclaim 1 in an amount effective to accomplish said cleaning. 5.Azeotrope-like compositions consisting essentially of from about 89 toabout 99 weight percent 1-bromopropane; from about 1 to about 11 weightpercent nitromethane; and, based on the total weight of said1-bromopropane and nitromethane, from about 5 to about 25 weight percent2-propanol wherein said compositions boil at about 64.9° C.±about 2.0°C. at 760 mmHg.
 6. The azeotrope-like compositions of claim 5 consistingessentially of from about 92 to about 99 weight percent 1-bromopropane;from about 1 to about 8 weight percent nitromethane; and, based on thetotal weight of said 1-bromopropane and nitromethane, from about 7 toabout 20 weight percent 2-propanol wherein said compositions boil atabout 64.9° C.±about 1.0° C. at 760 mmHg.
 7. The azeotrope-likecompositions of claim 5 consisting essentially of about 95 weightpercent 1-bromopropane; about 5 weight percent nitromethane; and, basedon the total weight of said 1-bromopropane and nitromethane, from about10 to about 15 weight percent 2-propanol wherein said compositions boilat about 64.9° C.±about 0.5° C. at 760 mmHg.
 8. A method for cleaning asurface of a substrate which comprises treating said surface with acomposition of claim 5 in an amount effective to accomplish saidcleaning.
 9. Azeotrope-like compositions consisting essentially of fromabout 65 to about 92 weight percent 1-bromopropane; from about 8 toabout 35 weight percent acetonitrile; and, based on the total weight ofsaid 1-bromopropane and acetonitrile, from about 1 to about 35 weightpercent 2-methyl-2-propanol wherein said compositions boil at about64.1° C.±about 2.0° C. at 760 mmHg.
 10. The azeotrope-like compositionsof claim 9 consisting essentially of from about 75 to about 90 weightpercent 1-bromopropane; from about 10 to about 25 weight percentacetonitrile; and, based on the total weight of said 1-bromopropane andacetonitrile, from about 4 to about 32 weight percent2-methyl-2-propanol wherein said compositions boil at about 64.1°C.±about 1.0° C. at 760 mmHg.
 11. The azeotrope-like compositions ofclaim 9 consisting essentially of about 82 weight percent1-bromopropane; about 18 weight percent acetonitrile; and, based on thetotal weight of said 1-bromopropane and acetonitrile, from about 6 toabout 30 weight percent 2-methyl-2-propanol wherein said compositionsboil at about 64.1° C.±about 0.5° C. at 760 mmHg.
 12. A method forcleaning a surface of a substrate which comprises treating said surfacewith a composition of claim 9 in an amount effective to accomplish saidcleaning.
 13. Azeotrope-like compositions consisting essentially of fromabout 65 to about 92 weight percent 1-bromopropane; from about 8 toabout 35 weight percent acetonitrile; and, based on the total weight ofsaid 1-bromopropane and acetonitrile, from about 5 to about 30 weightpercent ethanol wherein said compositions boil at about 60.2° C.±about2.0° C. at 760 mmHg.
 14. The azeotrope-like compositions of claim 13consisting essentially of from about 75 to about 90 weight percent1-bromopropane; from about 10 to about 25 weight percent acetonitrile;and, based on the total weight of said 1-bromopropane and acetonitrile,from about 10 to about 25 weight percent ethanol wherein saidcompositions boil at about 60.2° C.±about 1.0° C. at 760 mmHg.
 15. Theazeotrope-like compositions of claim 13 consisting essentially of about82 weight percent 1-bromopropane; about 18 weight percent acetonitrile;and, based on the total weight of said 1-bromopropane and acetonitrile,from about 15 to about 21 weight percent ethanol wherein saidcompositions boil at about 60.2° C.±about 0.5° C. at 760 mmHg.
 16. Amethod for cleaning a surface of a substrate which comprises treatingsaid surface with a composition of claim 13 in an amount effective toaccomplish said cleaning.